The invention relates to a method of configuring an open end of a seamless or one-piece can body to be used for beverage cans, preserved food cans and so on, to form a necked-in and flange portion therein.
There is proposed a method of forming the necked-in portion and the flange portion simultaneously in the open end of the one-piece can body by a spinning method in U.S. Pat. Nos. 4,563,887 and 4,760,725.
The forming tool used in the prior art, is provided with a can end holder or collar driven for rotation about its axis, an anvil or sleeve and a spinning roll. The can end holder is resiliently biased toward the sleeve which is at an axially fixed position. The sleeve has a smaller diameter than that of the can end holder, and is orbited to its eccentric position so that it may be in contact with the inside wall of the open end while the open end is shaped.
The can body whose open end is forced onto the collar is rotated about its axis by the can end holder and a bottom chuck cooperating therewith.
While the spinning roll is radially forced into the open end against a V-shaped recess formed between the can end holder and the anvil, the open end is squeezed between the spinning roll and the anvil to form the necked-in portion, and the foremost end is pressed against the can end holder resiliently by the spinning roll which is moving toward the collar, to form the flange portion.
The prior method has disadvantages that the outer lacquer film on the configured portion is susceptible to damages such as peeling due to slippage between the open end and the spinning roll, and the shaped portion is liable to be reduced in its thickness to the extent that rupture might occur, owing to the squeezing and pressing, particularly when a relatively thin open end is spin-formed at a relatively high velocity, so as to reduce material and operation costs.